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Re: How can I change a variable in a equation when use "solve"?
Posted:
Apr 4, 2013 9:20 PM


On 4/4/2013 5:17 PM, Jingzhou Wang wrote: > Dear all, > > A question about using the solve function. My code is as follows, > > syms a x y > s = solve('x*exp(x)=y, y=ax','x,y') > s = [s.x s.y] > > It works when I use a number such as "2" instead of "a" in the equation >'y=ax'. But when I include the variable in the equation, it doesn't go. >Since I want to change the "a" value outside the "solve" function, how can I do this? > > The matlab version is R2010a. > > Many thanks! > > Jing >
There is no algebraic solution for x
 EDU>> syms x y a EDU>> sol=solve(x*exp(x)==ax,x) Warning: Explicit solution could not be found. > In solve at 179 
when you put a number for 'a', then matlab must have used numerical root finding to solve it
EDU>> sol=solve(x*exp(x)==2x,x) 0.6748316143423993509028640916966
I hope you know that not every equation have closed form solution.
Nasser



